Liquid crystal display devices used in portable electronic appliances such as mobile telephones conventionally include charge-pump power-supply circuits for generation of supply voltages necessary for driving the display devices. Also conventionally, for reduced power consumption in the display devices, such liquid crystal display devices as described sometimes employ a driving method in which gate lines serving as scanning signal lines are scanned and a display image is refreshed in a scanning period (also called “charging period” or “refreshing period”) and thereafter all the gate lines are brought into a non-scanning state and the refreshing is stopped in an intermission period (also called “holding period” or “non-refreshing period”. This driving method is called, for example, “intermission driving”, and is also called “low-frequency driving” or “intermittent driving”.
In order to reduce power consumption sufficiently in the liquid crystal display device which uses the intermittent driving, it is also necessary to reduce power consumed by the charge-pump power-supply circuit. As a solution, there is proposed a liquid crystal display device (See Patent Document 1 for example) in which a charge-pump power supply circuit has a reduced pump operation frequency in the non-scanning period than in the scanning period.
There is another arrangement proposed: A liquid crystal drive circuit has a power supply source provided by a voltage boosting circuit device in which a clock signal is supplied as a drive signal to the voltage boosting circuit when the liquid crystal drive circuit has a large consumption current, whereas the voltage boosting circuit stops its operation and a drive signal level is fixed when the liquid crystal drive circuit has a small consumption current (See Patent Document 2 for example).